(a) Prohibition. Effective September 1, 1995, an insurer or agent may not use an underwriting guideline for private passenger automobile insurance based, in whole or in part, on whether an insured or applicant purchases types or amounts of coverage in excess of the minimum automobile liability coverage required to show proof of financial responsibility under the Motor Vehicle Safety Responsibility Act, Transportation Code, Chapter 601. The failure to comply with this section constitutes an unfair trade practice in the business of insurance in violation of Insurance Code Chapter 541, and is subject to the provisions thereof.(b) Definition of "Underwriting Guideline." For the purposes of this rule, an "underwriting guideline" is a rule, standard, marketing decision, guideline, or practice, whether written, oral or electronic, used by an insurer or its agent to examine, bind, accept, reject, renew, non-renew, cancel or limit coverages made available to classes of consumers.(c) Definition of "Private Passenger Automobile Insurance." For the purposes of this rule, "private passenger automobile insurance" is the insurance for which a personal auto policy is issued.